1. Field of the Invention
The present invention relates to a semiconductor device, more particularly to an SPnT (Single-Pole-n-Throw) switch (1 input n outputs switch) (n is 1 or a higher integer) or an nPST (n-Pole-Single-Throw) switch (n inputs 1 output switch) (n is 1 or a higher integer) using a GaAs MESFET (MEtal Semiconductor Field Effect Transistor).
2. Description of the Related Art
In a high frequency switch device which directly switches high frequency signals from several MHz to several tens GHz, a mechanical switch (relay) and a semiconductor switch are known. A semiconductor switch is widely used in the mobile communication field because of such features as high-speed switching, compactness, light weight and superb reliability. Particularly an SPDT (Single-Pole-Dual-Throw) switch (1 input 2 outputs switch) using a GaAs MESFET, which has such features as high-speed operation and in theory almost zero power consumption, is widely used for the antenna selector switch of a mobile communication terminal and other components which demand compactness and light weight.
Now a conventional semiconductor switch will be described with reference to FIG. 1.
FIG. 1 is a circuit diagram depicting a unit switch comprised of an SPST (Single-Pole-Single-Throw) switch, which constitutes a conventional SPnT switch.
As FIG. 1 shows, the SPnT switch is normally comprised of n number of unit switches 16 further comprising a through FET 11 where one of the source electrode and the drain electrode is connected to the input terminal, and the other is connected to the output terminal, and a shunt FET 12 where one of the source electrode and the drain electrode is connected to the output side of the through FET 11 and the other is grounded. The through FET 11 is a transfer gate, and the shunt FET 12 is disposed for improving isolation between input and output. In FIG. 1, 13A and 13B are the bias resistors for preventing the leakage of high frequency signals into the control terminals 14A and 14B.